xgl: Add new resource type for textures

This change modifies xgl.h to include a new descriptor set
slot type for textures, distinct from resources:

    XGL_SLOT_SHADER_TEXTURE_RESOURCE

Buffers continue to use:

    XGL_SLOT_SHADER_RESOURCE

The ordering of their inclusion in binding tables entries is
important: textures must come before buffers.  This is how
the compiler expects them to be laid out.
diff --git a/icd/intel/pipeline.h b/icd/intel/pipeline.h
index aa5845a..fbc0390 100644
--- a/icd/intel/pipeline.h
+++ b/icd/intel/pipeline.h
@@ -69,6 +69,7 @@
     /* this is not an intel_obj */
 
     XGL_UINT rt_count;
+    XGL_UINT texture_resource_count;
     XGL_UINT resource_count;
     XGL_UINT uav_count;
     XGL_UINT sampler_count;